STUDIES ON THE CEREAL ECOSYSTEM
123
than that emerging from cultivated fields (a = 8). Some of these
differences were due t o cultivation; for example, the pre-pupae of the
sawflies of the genus Dolerus are vulnerable to desiccation and damage
during autumn cultivations. Other differences are due to the presence
of grass-clover mixtures in the crop before harvest as well as after
harvest. The proportion of predatory insects emerging from the undersown sites was much higher (42.8% cf. 27.6%); we are now comparing
the fauna of undersown leys with that of direct reseeded leys.
SITE (5)
SITE (6)
1969
Spring barley
not undersown
I
+
MCPA, Dicamba, CMPP
Stubble and straw burnt
Periodic cultivations
and ploughed twice
3.
3.
Spring barley undersown
with Phleum, Festuca
and Trifolium
MCPA 2,4-DB
Stubble grazed by sheep
No cultivations
3.
4
3.
Traps operated 1 March-1 June 1970
SITE (7)
SITE (8)
1970
Spring barley
Spring barley undersown
with Lolium (523, 524,
RVP) and Trifolium
26 May MCPA, 2,4-DB
Stubble grazed by cattle
No cultivation
J.
1
. 1
23 May MCPA, 2,4-DP
Straw baled and removed
Chisel plough and plough
. 1'
3.
3.
Traps operated 1 March-1 June 1971
c. T H E R E L A T I O N S H I P B E T W E E N F A U N A L A N D
F L O R A L D I V E R S I T Y
The fauna of 'three floristically diverse fields has been compared with
that of three weed-free fields. All the fields were sown with spring barley,